1. Field of the Invention
This invention relates to a means for leveling a drill or similar apparatus with respect to two or three orthogonal directions.
2. Description of the Prior Art
Several attempts have been made in the past to level drills and the like with bubble indicators. For example, the patent to Moulton, U.S. No. 1,333,559 discloses an "Attachment for Drills". The attachment comprises a pair of level sight gauges arranged at right angles to one another. The object of the device is to hold the drill at right angles with respect to the working surface.
The patents to Schtabe, U.S. No. 960,718 and Kennedy, No. 2,541,366 are directed towards the attachment of two or three levels for use with manual drills. Occasionally tubular levels are incorporated in the frame of the device that supports the drill. Such a device is available from Sears Roebuck and Company where the tubular level is incorporated into the portable work bench that holds the drill. The device is known as a Drill Guide, Catalog No. 9 GT 51726 and it includes adjustments so that a drill can be set at angles with 5.degree. increments between 0.degree. and 90.degree..
Tubular levels are also found in the context of electrical devices other than drills. For example, the patent to Bogdan, U.S. No. 3,540,122 describes a "Hedge Trimmer and Leveling System for Same". In that reference two tubular levels are built into the hedge trimmer and located in directions perpendicular to each other so as to allow the user to correctly orient the hedge trimming apparatus.
In general the prior art devices are moderately complicated and frequently bulky. The device described in U.S. Pat. No. 960,718, for example, is almost as large and cumbersome as the mechanical drill to which it is attached. Moreover, it has been found that the use of two or more tubular levels at one time is difficult to coordinate. While the eye follows the bubble in one level, it has been found, that the bubble in the other level tends to drift. These and other problems associated with the prior art have been overcome by the invention described in this disclosure.